Has anyone had any problems with there in injectors stuck open when running? my xj the upstream o2 is running rich! also i got back firing in the intake!

any ideas????

 

I had one that I damaged changing O-Rings, don't ask, anyway it started and ran with a miss at idle and smoothed out at mid rpm and wide open.
Not really any popping back through the intake.
I was just lucky enough that when I pulled them I can see one looked different than the others in that the tip looked wet compared to the others. The engine was still very warm when I pulled them.

 

Intake manifold leak - puts too much O2 on the exhaust, ECM richens it too much, end result is rich.
Do a smoke test to find the leak.

 

How do u do a smoke test?